The Red Devils reportedly submitted a £20million bid last week but could now see the offer challenged as Spanish paper Mundo Deportivo revealed that Barcelona are also in the hunt for the German international.

The Catalan club are claimed to be readying a bumper contract offer in order to lure the 25-year-old to replace Barca legend Carles Puyol at the Nou Camp.

Barcelona boss Luis Enrique has already added Ivan Rakitic, Claudio Bravo, and Marc-Andres red Stegen to his squad after the Blaugrana underwhelmed in both La Liga and the Champions League last season.

But United boss Louis van Gaal is extremely keen on bringing Hummels to Old Trafford, which could lead to a bidding war between the two clubs.

The German international is in high demand after impressing with Borussia Dortmund as well as for Germany, scoring two important World Cup goals.